linux.git/arch/arm/kernel/entry-ftrace.S, branch for-next

ARM: 9382/1: ftrace: Define ftrace_stub_graph

2024-04-18T11:12:18+00:00

Several architectures defines this stub for the graph tracer,
and it is needed for CFI, as it needs a separate symbol for it.
The trick from include/asm-generic/vmlinux.lds.h to define
ftrace_stub_graph to ftrace_stub isn't working when using CFI.
Commit 883bbbffa5a4 contains the details.

Tested-by: Kees Cook 
Signed-off-by: Linus Walleij 
Signed-off-by: Russell King (Oracle)

ARM: ftrace: enable the graph tracer with the EABI unwinder

2022-02-09T08:13:59+00:00

Enable the function graph tracer in combination with the EABI unwinder,
so that Thumb2 builds or Clang ARM builds can make use of it.

This involves using the unwinder to locate the return address of an
instrumented function on the stack, so that it can be overridden and
made to refer to the ftrace handling routines that need to be called at
function return.

Given that for these builds, it is not guaranteed that the value of the
link register is stored on the stack, fall back to the stack slot that
will be used by the ftrace exit code to restore LR in the instrumented
function's execution context.

Signed-off-by: Ard Biesheuvel 
Reviewed-by: Steven Rostedt (Google)

ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST

2022-02-09T08:12:33+00:00

Fix the frame pointer handling in the function graph tracer entry and
exit code so we can enable HAVE_FUNCTION_GRAPH_FP_TEST. Instead of using
FP directly (which will have different values between the entry and exit
pieces of the function graph tracer), use the value of SP at entry and
exit, as we can derive the former value from the frame pointer.

Signed-off-by: Ard Biesheuvel 
Reviewed-by: Steven Rostedt (Google)

ARM: ftrace: avoid unnecessary literal loads

2022-02-09T08:12:33+00:00

Avoid explicit literal loads and instead, use accessor macros that
generate the optimal sequence depending on the architecture revision
being targeted.

Signed-off-by: Ard Biesheuvel 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Steven Rostedt (Google)

ARM: ftrace: avoid redundant loads or clobbering IP

2022-02-09T08:12:32+00:00

Tweak the ftrace return paths to avoid redundant loads of SP, as well as
unnecessary clobbering of IP.

This also fixes the inconsistency of using MOV to perform a function
return, which is sub-optimal on recent micro-architectures but more
importantly, does not perform an interworking return, unlike compiler
generated function returns in Thumb2 builds.

Let's fix this by popping PC from the stack like most ordinary code
does.

Signed-off-by: Ard Biesheuvel 
Reviewed-by: Steven Rostedt (Google)

ARM: ftrace: use trampolines to keep .init.text in branching range

2022-02-09T08:12:32+00:00

Kernel images that are large in comparison to the range of a direct
branch may fail to work as expected with ftrace, as patching a direct
branch to one of the core ftrace routines may not be possible from the
.init.text section, if it is emitted too far away from the normal .text
section.

This is more likely to affect Thumb2 builds, given that its range is
only -/+ 16 MiB (as opposed to ARM which has -/+ 32 MiB), but may occur
in either ISA.

To work around this, add a couple of trampolines to .init.text and
swap these in when the ftrace patching code is operating on callers in
.init.text.

Signed-off-by: Ard Biesheuvel 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Linus Walleij 
Reviewed-by: Steven Rostedt (Google)

ARM: ftrace: use ADD not POP to counter PUSH at entry

2022-02-09T08:12:32+00:00

The compiler emitted hook used for ftrace consists of a PUSH {LR} to
preserve the link register, followed by a branch-and-link (BL) to
__gnu_mount_nc. Dynamic ftrace patches away the latter to turn the
combined sequence into a NOP, using a POP {LR} instruction.

This is not necessary, since the link register does not get clobbered in
this case, and simply adding #4 to the stack pointer is sufficient, and
avoids a memory access that may take a few cycles to resolve depending
on the micro-architecture.

Signed-off-by: Ard Biesheuvel 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Linus Walleij 
Reviewed-by: Steven Rostedt (Google)

ARM: ftrace: ensure that ADR takes the Thumb bit into account

2022-02-09T08:12:32+00:00

Using ADR to take the address of 'ftrace_stub' via a local label
produces an address that has the Thumb bit cleared, which means the
subsequent comparison is guaranteed to fail. Instead, use the badr
macro, which forces the Thumb bit to be set.

Fixes: a3ba87a61499 ("ARM: 6316/1: ftrace: add Thumb-2 support")
Signed-off-by: Ard Biesheuvel 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Steven Rostedt (Google) 
Reviewed-by: Linus Walleij

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

2019-06-19T15:09:55+00:00

Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Enrico Weigelt 
Reviewed-by: Kate Stewart 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman

ARM: 8788/1: ftrace: remove old mcount support

2018-09-19T09:44:50+00:00

Commit cafa0010cd51 ("Raise the minimum required gcc version to 4.6")
raised the minimum GCC version to 4.6. Old mcount is only required for
GCC versions older than 4.4.0. Hence old mcount support can be dropped
too.

Signed-off-by: Stefan Agner 
Signed-off-by: Russell King